Grizzly bears and calving caribou: what is the relation with river corridors?

Article Abstract:

The effect of the Trans-Alaska Pipeline on caribou of the central Arctic herd has been discussed since the 1970s. Some previous studies suggest that cows and calves avoid the areas surrounding the pipeline because of human disturbance, while others indicate female avoidance of river corridors is linked to the increased abundance of grizzly bears and wolves. A new investigation seeks to determine the link between caribou cow and grizzly bear use of river corridors on the calving grounds of the Arctic National Wildlife Refuge. The research shows that cows and calves do not avoid river corridors, which contain similar distributions of grizzly bears as nonriverine areas.

Environmental aspects, Arctic National Wildlife Refuge, Alaska, Trans-Alaska Pipeline

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Grizzle bear predation rates on caribou calves in northeastern Alaska

Article Abstract:

Grizzly bears are important predators of ungulate calves but observations of predation rates are imprecise because of the difficulty in collecting accurate measurements. An investigation of the grizzly bears' predation rates on calves of the internationally important Porcupine Caribou Herd is presented. Continuous aerial observations show predation rates estimated at 2,000-3,000 calves annually, accounting for around 5-7% of the estimated 43,000 calves produced per year.

Patient outcomes, Mortality, Observations, Predation (Biology), Brown bear, Brown bears

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Evaluating growth of the porcupine caribou herd using a stochastic model

Article Abstract:

The survival and reproduction rates of Alaska's Porcupine Caribou herd is modelled as a stochastic process to determine the 'distribution of potential population rates of change.' The models, which cover the periods 1983-89 and 1989-92, showed that the growth rate was dependent on perturbations to adult female survival and calf survival. As such, petroleum extraction on calving grounds or changes in calving habitats are likely to impact the herd's population.

Models, Animal populations, Stochastic processes

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